Thermal characteristics are critical considerations in any integrated circuit design process. Thermal characteristics are particularly important to the design of packaged integrated circuit devices, such as high performance integrated circuits including microprocessors (e.g., the AMD K-7 Athlon® processor, Intel Pentium4® processor, etc.). A device with less than optimum thermal characteristics can cause device or die failures and/or package failures.
Thermal characteristics over a lot of packaged integrated circuit dies can vary, causing a corresponding variability in device performance. Thermal designs seek to reduce the thermal characteristic variations within the package for consistent and reliable performance.
Generally, one particular thermal characteristic, the thermal transfer function θ(ω), can be used to approximate the thermal response of a packaged integrated circuit die. Heretofore, the thermal transfer function has been approximated by collecting temperature readings from a thermal die while power is supplied to it. The thermal die is a replica of the actual integrated circuit die and is typically the same size as the integrated circuit die. The thermal die, however, does not include the circuitry of the integrated circuit but merely approximates the thermal transfer function of the integrated circuit die. The thermal die typically includes resistors for duplicating the power dissipation of the integrated circuit die. Accordingly, it cannot approximate or indicate variations in the thermal transfer function across a lot of dies.
To determine the thermal transfer function, the thermal die is placed in a test fixture and provided power across a spectrum of power levels. The temperature of the thermal die is measured with a thermocouple sensor or embedded on-die sensor, i.e. thermistor or diode, across the spectrum of power levels by conventional equipment to determine the thermal transfer function. The thermal transfer function is utilized for approximations associated with the design and packaging of the integrated circuit die.
As discussed above, the use of the thermal die does not allow the measurement of the actual thermal transfer function of an integrated circuit die. Accordingly, there is a need for a method for determining thermal characteristics of an actual packaged integrated circuit die. Further still, there is a need for using the actual thermal characteristics of the device for feed forward control of temperature in the device. Even further still, there is a need for in situ transient thermal characterization of a live device.
Yet further still, there is a need for determining the thermal transfer function or thermal response in the frequency domain for a packaged device. Even further, there is a need for a simple and yet effective system for and method of measuring thermal characteristics of an integrated circuit die. Further still, there is a need for a low cost system and method of thermally characterizing a packaged integrated circuit.